Objective: To evaluate the Bolton ratio in the Maratha population in Pune with near ideal occlusion. Materials and Methods: Fifty study casts were made from impression obtained from patients (25 males and 25 females) aged between 15 and 30 years visiting the Department of Orthodontics and Dentofacial Orthopedics at Sinhgad Dental College and Hospital, Pune. The mesiodistal widths of all maxillary and mandibular teeth from right first molar to left first molar were measured with a digital caliper to calculate the Bolton ratio. The readings were then used to compute the anterior and total Bolton ratios. t-test was used for the statistical analysis. Results: The mean overall and anterior ratios were found to be 92.73 and 80.48 with standard deviation of 2.69 and 2.86, respectively. The range of overall ratio was 81.91–96.75, and the range of anterior ratio was 74.75–86.45. The values obtained from this study indicated that there was a statistically significant difference between the overall and anterior ratios of Maratha and Caucasian participants. Conclusion: It can be suggested that new values should be obtained for the Maratha population as the values were found to be significantly different from the Bolton values obtained for Caucasian population. Hence, population-specific standards are necessary to be formed for clinical assessment.

Keywords: Bolton analysis, Maratha, Pune

How to cite this article:Patel YV, Nair VS, Jamenis SC. Bolton analysis of the maratha population in Pune. J Dent Allied Sci 2017;6:8-11

Malocclusion can be defined as a significant deviation from a normal or “ideal” occlusion.[1] Many components are involved in the achievement of a normal occlusion including skeletal, soft tissue, and local dental factors. Andrews' study [1] was based on 120 casts of nonorthodontic patients in which he found six significant characteristics:

Molar relationship

Correct crown angulation

Correct crown inclination

No rotations

No spaces and tight contact points

Flat occlusal plane.

Bennett and McLaughlin [2] added a seventh key which was correct tooth size. To achieve a good occlusion with satisfactory intercuspation of the teeth and a correct overjet and overbite, the maxillary and mandibular teeth must be proportional in size. A tooth size discrepancy (TSD), defined as a disproportion among the sizes of individual teeth, will affect attainment of an ideal occlusion. The term “tooth size” refers to the mesiodistal widths of the teeth. TSD should be taken into account when treatment is planned since they are a principal factor in accurate space analysis. Black [3] developed tables for average tooth sizes. In the research that followed, different approaches were developed for interarch tooth size analysis.[3],[4],[5],[6],[7],[8]

There have been several studies suggesting methods of defining and measuring TSD,[9],[10],[11],[12] but the best-known study of TSD in relation to the treatment of malocclusion was proposed by Bolton [13] in 1958. Bolton developed two ratios for estimating TSD by measuring the summed mesiodistal widths of the mandibular to the maxillary anterior teeth (anterior ratio) and the total width of all lower and upper teeth from right first molar to left first molar (overall or total-arch ratio).

Most of the previous studies were performed on casts of Caucasians, regardless of the ethnicity or sex of the participants. Smith et al.[14] stated that Bolton's ratios were only applicable to white females and therefore should not be applied indiscriminately to white males, blacks, or Hispanics. Several pieces of evidence indicate that tooth size ratios show ethnic, racial, and sex differences.[15],[16] Various studies have investigated ethnic and sex [17],[18],[19] differences in the intermaxillary tooth ratios. In fact, tooth development is a matter of both genetic and environmental factors.

The aim of this study was to calculate both the anterior and overall ratios for a sample of 50 (25 males and 25 females) Maratha dentitions and to compare these ratios with the original data from Bolton's study.

Materials and Methods

Dental casts of 50 participants (25 males and 25 females) aged between 15 and 30 years were obtained from the patients visiting the Department of Orthodontics and Dentofacial Orthopedics, at an institute in Pune. The sample size was determined using the mean and standard deviation values from the study conducted by Bolton.[13] The participants were selected by one operator only, and an informed consent was taken from each participant for the same. The casts were obtained from subjects belonging to Maratha caste, inhabiting Maharashtra and traced back to at least one generation. Maxillary and mandibular alginate impressions were made of the selected 50 participants and then poured in dental stone. The casts were retrieved and bases were fabricated. Digital caliper was used to measure the mesiodistal widths of the teeth to the nearest 0.01 mm of these study models, and the anterior and overall ratios were calculated.

Inclusion criteria

Maratha ancestors at least from one previous generation

Age: Between 15 and 30 years

All permanent teeth (excluding 3rd molars) should be present and fully erupted

Angle's Class I molar relation bilaterally, Class I canine relation bilaterally, and Class I incisor relation along with Andrew's six keys

All these factors affect the mesiodistal dimension of the teeth and hence the anterior and overall ratios.

To ensure measurement accuracy, 1 month later, 20 pairs of dental casts were randomly selected, and the mesiodistal tooth widths were again measured by the same investigator. The anterior and overall ratios were calculated using the same method. A paired t-test was applied to the first and second measurements. Random error was determined by calculating the standard deviation of the differences between the first and second measurements.

Calculations were made to see participants with anterior and overall tooth size discrepancies outside two standard deviations from the Bolton means and more than 1.5 mm of maxillary or mandibular correction. These measures were required to give the Bolton mean anterior and overall ratios.

The data were statistically analyzed for range, standard deviation, mean, and coefficient of variation. Unpaired t-test was applied to draw a distinction between the results of this study and the results from Bolton's study.

Results

The mean overall and anterior ratios were found to be 92.73 and 80.48, respectively, with standard deviation of 2.69 and 2.86, respectively. The range of overall ratio noted was 81.91–96.75, and the range of anterior ratio was 74.75–86.45. [Table 1] gives the descriptive statistics including the mean, standard deviation, and range of the anterior and overall ratios for the participants. [Table 2] shows the comparative analysis between Maratha males and females. [Graph 1] gives the comparison of the overall and anterior ratios between the present study and Bolton's results.[13] A statistically significant difference was noted in the anterior and overall ratios derived from the present study as compared to the values from Bolton's study. Both anterior and overall ratios were on the higher side as shown in [Table 1].

Table 1: Statistical comparison of the overall and anterior ratios between the present study and Bolton's results (1958)

Multifactorial etiology has been attributed to dental crowding or spacing in permanent dentition. One such factor is the mesiodistal tooth width discrepancy.[20] The importance of TSD in orthodontic diagnosis has been widely reported in literature and accepted by the orthodontic community.

Several studies have reported differences in mesiodistal tooth width in crowded and noncrowded dentitions of different populations and sexes in the world, by considering mesiodistal width of individual tooth rather than considering the whole arch.

Bolton [13] developed two ratios for estimating TSD by measuring the summed mesiodistal widths of mandibular to maxillary anterior teeth and the total width of all lower to upper teeth from right first molar to left first molar. He concluded that an overall ratio of 91.3 and an anterior ratio of 77.2 were necessary for proper coordination of the maxillary and mandibular teeth. Bolton's original research was carried out on 55 Caucasian female cases with excellent occlusions out of which 44 were orthodontically treated and 11 were nonorthodontically treated, and so its application to males, non-Caucasian populations, and different malocclusion groups has been questioned. The prevalence of Bolton's tooth size discrepancies in different racial and malocclusion groups has been studied extensively for a number of populations, and the studies have generated varying results.

Lavell [8] reported that Negroids had greater overall and anterior ratios than Caucasoids and Mongoloids and that the overall ratio was consistently greater in males than in females, regardless the racial origin. Smith et al.[14] concluded that Bolton's ratios were only applicable to white females and therefore should not be applied indiscriminately to white males, blacks, or Hispanics. Smith et al. also stated that the overall ratio was significantly larger in males than in females. Thus, the generalized use of the Bolton analysis and the proposed values for a harmonious dentition are under discussion and might not be valid for other populations.

This study is designed to evaluate tooth width ratios in noncrowded, near ideal, and nontreated occlusions of the Maratha population. A total of 50 participants (25 males and 25 females) aged between 15 and 30 with Angle's Class I molar relation, Class I canine relation, and Class I incisor relation having all permanent teeth except the 3rd molar with no crowding and residual crown and bridge restorations, no tooth deformity or supernumerary teeth, and no severe mesiodistal or occlusal tooth attrition were selected for the study.

Accurate dental casts of all the participants were made, and each tooth was measured at the largest mesiodistal dimension using a caliper accurate to 0.01 mm, and the total and anterior tooth size ratio was computed for each participant using Bolton's tooth size analysis. Data collected were subjected to statistical analysis using t-test.

The result of the present study shows significant difference in anterior as well as overall ratios of the Maratha population as compared to Bolton's ratios of Caucasians females. It also shows that there is a statistically significant difference between the overall ratio between males and females and that the overall ratio is higher in males than in females.

The overall ratio among the Maratha population ranged from 81.91 to 96.75, a mean value of 92.73 with a standard deviation of 2.69, whereas in Caucasian population, overall ratio showed a range of 87.5–94.8, a mean of 91.30 with standard deviation of 1.91 which shows that our values are greater than that of original Bolton's Caucasian female population. Anterior ratio among the Maratha population ranged from 74.75 to 86.45, a mean of 80.48 with standard deviation of 2.86 whereas Caucasian females had a range of 74.5–80.4, a mean of 77.20 with standard deviation of 1.65 which shows that our values are greater than that of original Bolton's Caucasian female population.

The overall ratio is found to be higher in males than in females with a statistically significant difference with a P value of 0.0308 while the anterior ratio is not statistically significant between males and females.

In summary, our results agree with the results of a study done by Smith et al.[14] on three populations of whites, blacks, and Hispanics which showed that overall and anterior ratios of the three populations differed significantly from Bolton's values. On this basis of the foregoing, it is clear that the Bolton's ratios are not applicable across all populations. Separate standards for different populations are needed. Further research should be done to standardize the norms for the Maratha population separately for both males and females.

Conclusion

In general, the values obtained from this study for the Maratha population differ from the data of Caucasian population. It can be inferred that Bolton's values cannot be used in the Maratha population. Hence, population-specific standards are necessary for clinical assessment.